Tripack film with emulsion layers adjacent each other and method of making same



Feb. 17, J Q CRAWFORD TRIPACK FILMS WITH EMULSION LAYERS ADJACENT EACH OTHER AND METHOD OF MAKING SAME Filed June 22, 1944 GEEL-N SENS/ 771/6' D FIG l i \\\\\\\\\\\\\\\\\\\Q@mm/Emmer FIG'Z FIG 3 wum JACK C CRAWFORD AMW,

Patented Feb. 17, 1948 TRIPACK FILM WITH EMULSION LAYERS ADJACENT EACH OTHER AND METHOD 0F MAKING SAME Jack C. Crawford, United States Navy, Anacostia, D. C.

Application June 22, 1944, Serial No. 541,557

3 Claims. (Cl. 95-2) (Granted under the act of March 3, 1883, as amended April 30, 1928; 370 0. G. 757) l This invention relates to a photographic film, and more particularly to a lm incorporating a plurality of light sensitive emulsion layers, adapted to the production of pictures in natural colors.

The term lm, as employed herein, refers to next green sensitive and the other red sensitive, or

panchromatic. The diiiiculties which to date have prevented the development of a successful tripack are largely mechanical in nature. The problem is to support all three of the emulsion layers on the film base without the employment of intervening layers of other material, the arrangement of the emulsion layers being such that the image formed in each upon exposure may thereafter be fixed upon an individual supporting base without loss of registry or impairment of the image. Experience has shown that the placing of even the thinnest of supporting layers between the emulsion layers distorts the light rays entering the next adjacent emulsion layer, with resulting loss in sharpness of definition.

It is an object of this inventio-n to overcome the aforesaid and other difficulties and to supply a satisfactory tri-pack film. A further object is to supply a film of this type wherein the emulsion layers are placed adjacent each other without intervening supporting layers. Still another object is to provide a tri-pack lm so arranged `that the image formed in each of the three light sensitive emulsion layers upon exposure of the film, may be fixed or joined to an individual supporting base in such fashion as later to permit the picture to be printed in natural colors without loss of registry and with sharpness of image.

It is my invention that the forego-ing objects may be attained by an arrangement whereby three light sensitive emulsion layers are sandn wiched together between two transparent bases of Celluloid or like material, as illustrated in Fig, l of the accompanying drawings, wherein:

Fig. l is a cross sectional View, to an enlarged scale, taken through one edge of the film;

Fig. 2 is a cross sectional view, to an enlarged scale, taken through one edge of the blue sensitive layer and its transparent base support, the emulsion havingbeen separated from the adja- 2 cent green sensitive emulsion layer during an iniiial step of processing the film for development; an

Fig. 3 is a cross sectional view, to an enlarged scale, taken through one edge of the green and red sensitive emulsion layers and showing each emulsion layer being joined to a transparent base support, the green sensitive emulsion layer having been joined to its base support after the removal of the emulsion from the developing and stop solutions.

In the drawings, the transparent support bases i0 and Il are positioned at the front and rear sides of the film respectively (Fig, l). By the front side Iof the film is meant the side through which the light first enters, as shown by the arrow in Fig. 1. The transparent supporting lay- `ers are usually composed of Celluloid or of a suitable transparent plastic material.

In fabricating the film, the blue sensitive emulsion layer I2, containing a yellow dye, is coated on the inner surface of the base iS. The yellow dye serves to prevent the light rays in the blue portion of the spectrum from penetrating the blue sensitive emulsion layer to more than a slight depth, with the result that the modification of the silver particles in thisemulsion layer caused by exposing the film is confined to the region of the emulsion adjacent the film base Hl. This condition is favorable to the formation of a good silver gelatin relief image from this portion of the film. The support lli, with the applied emulsion layer I2, forms the front ele'- ment of the film.

A red sensitive, or panchromatic, emulsion layer i3, which is last exposed to the light, is coated in similar fashion on the inner, or frontward, surface of the base member Il, This emulsion layer I3 is then desensitized downwardly in suitable manner, as by the application of a potassium iodide solution to the fr-ontward surface 13a. This method is disclosed by Seymour in U. S. Patent No. 1,946,640. As a result of this treatment, the silver particles in emulsion layer i3 ywhich are modified on exposure are 'those which are located at or near the boundary between the emulsion and the base member H, thus making it possible to form a goed relief image with reference to this emulsion layer.

A green sensitive emulsion layer I4, containing a red dye, is then coated on top of the red sensitive emulsion layer i3 after the latter has been subjected to the desensitization treatment. The red dye acts as aV filter for the following red sensitive, vor -panchrom-atic, emulsion layer i3, and it also restrains the green light from penetrating deeply into the emulsion layer I 4. Accordingly, the exposure in the emulsion layer I4 is held to the surface regions thereof adjacent the emulsion layer I 2, thisl condition being that desired for forming a good silver gelatin relief image from the green sensitive emulsion layer. It may be.

a removable anti-halation coating I 5 whichserves'.

to improve the quality of the image. This coating may be removed in the usual fashion during the developing process.

The front and rear elementsxof the film are then connected to each other by joining the open sidesof the blue sensitive and the green sensitive emulsionlayersby means of a suitable adhesive I6. The thickness of this adhesive layer is sok small as to befhardly perceptible, and it causes no distortion of the light rays passing through it. The strength ofthe bond formed by theradhesiveshould be less than that existing either between. the emulsion layer I2 and the base member ID, or between the emulsion layers I3 and I4 or the emulsion I3 and its support II. Further, the strength of the adhesive should be suoli` that while the emulsionlayers I2 and lil are held rmly together byl it under normal conditions of usage of the lm, the front and rear elements of the film may readily be peeled apart by hand during the processing of the exposed film., It has been found that polyvinyl acetate provides an adhesive bond of satisfactory character for this purpose, though other substances now known and used in similar fashion in the art would perform equally well.

In certain instances it may be possible to eliminate the use of the adhesive where the front and rear film elements may otherwise be held together in a satisfactory manner during exposure of the film, For example, the film components may be held firmly together between glass plates applied to the outer surfaces of the base supports Ivand II.

When the lm is used, it is exposed in the normal fashion. Afterk exposure, the blue sensitive emulsion layer is peeled away from the green sensitive emulsion layer at the adhesive boundary. Each of the two resulting lm strips is then developed. In the latter step, I prefer to employ a tanning developer incorporating sodium sulphate, as this type of solution prevents swelling of the gelatin and keeps it in good condition fortransfer. A developing solution which I have found to be satisfactory has the following composition, solution B being added to solution A on making up and using the developer:

After development the lms are placed for about two minutes in a short stop bath such as a solution of 5% by weight boric acid in water, after which the two portions of the film may be exposed to light without'harm. The above stepsare carried out in a dark room under suitable conditions of light.

As the next step in the process, a third base support I'I, see Fig. 3, carrying on one side a suitable sub` to receive the silver image from the green sensitive emulsion layer, is soaked in water and is squeegeed down onto the surface of the green sensitive emulsion layer, the side of the base sup pori; I'I carrying the sub being placed adjacent they emulsion. In a few minutes the resulting iilm. portion incorporating the green and red sensitive emulsion layers is submerged in hot water` for a period, usually about 1 to 5 minutes, in order to dissolve the unhardened gelatin lying between the base layers II and Il. The latter are then pulled apart, leaving the green relief image on the new support I'I and the red relief image adhering to its original base I I.

All three of the base supports I0, II' and I'I are then washed free of any remaining unhardened gelatin with hot waterafter which the images thereon are xed in an acid hardening. fixing bath, and then washed and dried.

The resulting nlm strips are termed negative relief images. The processes for making three color transparencies or three color prints onpaper from the negative relief images are well known in the art and need not here be described. 'I'he details of such procedures are fully described in various publications, one such publication, for example, being that of theEastman Kodak Company, Rochester, New York, entitled Color Printing, with Eastman Wash-Off Relief Film.

The invention describedherein may be manu-'- factured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

Other modifications and changes in the number and arrangement of the parts may be made by those skilled in the art without departing from the nature of the invention, within the scope of what is hereinafter claimed.

I claim:

l. As a new article of manufacture, a tri-pack film consisting of two elements; the first element comprising a transparent reinforcing base through which the light first-enters the nlm, and a blue sensitive emulsion layer, containing a yel low dye, coated on the inner surface thereof; and the second element comprising a rear transparent supporting member forming the back of the film, said rear supporting member having an anti-halation material applied to its rearward surface, and having a panchrornatic emulsion layer coated on its frontwardsurface, said panchromatic layer being desensitized downwardly from its frontward surface .by suitable treatment, and a green sensitive emulsion'layer, containing a red dye, coated on said desensitized panchromatic emulsion layer; the two elements being joined together by a polyvinyl acetate adhesive of such characteristics that the elements ofthe film can be readily peeled apart by hand duringdevelopment of the lm, the juncture being eiectedbetween the open sides ofthe bluev sensitive and the green sensitive emulsion layers.

2. In a method of making a ilmincorporate three light sensitive emulsion layers, the steps comprising. applying aiirst emulsion layer to the rearward surface of a front transparent supporting member; applying a second emulsion layer to the frontward surface of a rear transparent supporting member; desensitizing downwardly from its frontward surface said second emulsion layer; coating a third emulsion layer 'upon the frontward surface of said desensitized emulsion layer; applying a polyvinyl acetate adhesive to the rearward surface of said rst emulsion layer and the frontward surface of said third emulsion layer, and joining said adhesive coated surfaces to form a unitary structure, the joint so formed being susceptible of rupture during the development process.

3. In a method of making a film incorporating three light sensitive emulsion layers, the steps comprising applying to the rearward surface of a front transparent supporting member as a rst emulsion layer, a blue sensitive emulsion containing a yellow dye; applying to the frontward surface of a rear transparent supporting member as a second emulsion layer, a panchromatic emulsion; desensitizing downwardly from its frontward surface said second emulsion layer; coating upon the frontward surface of said desensitized emulsion layer as a third emulsion layer, a green sensitive emulsion containing a red dye; and

bonding together with polyvinyl acetate the Iilm components so formed, said bond being formed between the rearward surface of said rst emulsion layer and the frontward surface of said third emulsion layer.

JACK C. CRAWFORD.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 927,244 Ives July 6, 1909 1,248,139 Lawshe Nov. 2'7, 191'? 1,261,542 Ives Apr. 2, 1918 1,306,904 Ives June 17, 1919 1,889,030 Ball Nov. 29, 1932 1,946,640 Seymour Feb. 13, 1934 1,951,043 Weaver Mar. 13,v 1934 1,966,653 Thornton July 1'7, 1934 2,112,226 Baldsiefen et al. Mar. 29, 1938 2,177,342 Hesser et al. Oct. 24, 1939 2,183,394 Gaspar Dec. 12, 1939 2,315,294 Sease Apr, 13, 1943 

